目前国内采用的围生期时间范围是( )
A.妊娠20周至产后l周
B.妊娠20周至产后2周
C.妊娠28周至产后l周
D.妊娠28周至产后2周
E.妊娠28周至产后3周
参考答案:C
—Can you hear ____?
—No, I can hear ____. [ ]
A. anything; nothing
B. anything; anything
C. something; nothing
D. something; something
在大气垂直结构中,云主要出现在()
A.对流层
B.平流层
C.中间层
D.热层